This invention is directed generally to telephone line test apparatus and more particularly to a novel in-line switched telephone line tester which may be interposed intermediate a modular telephone plug of an incoming line and a modular telephone jack of inside equipment, such as a private business exchange (PBX) system, which normally receives the incoming line directly, for testing the tip-ring polarity of the incoming line.
Briefly, modular telephone equipment currently in use utilizes a modular telephone receptacle or "jack" or socket capable of accepting a complementary modular telephone plug. Such a modular plug can be readily disconnected and connected to another similar modular jack at another location if desired. Certain telephone equipment, particularly of the "Touch-Tone" type, requires that the terminals or contacts of each receptacle or modular jack and its mating plug maintain the same, predetermined positive-to-negative polarity. More specifically, the polarity of the tip-ring voltage at the subscriber's end must be maintained with respect to the polarity thereof at the central office equipment. That is, a proper tip-ring voltage of proper polarity should appear at the incoming line to the customer's equipment.
It is possible that such modular plugs may inadvertently be miswired such that the tip-ring polarity contacts of the mating jack or receptacle are wired in the reverse polarity. Particularly with the advent of increasing customer or consumer purchased and owned and/or customer or consumer installed or PBX telephone equipment, such miswiring may occur. Moreover, it is important to determine whether any malfunctioning line is due to a malfunction in the customer-owned PBX equipment or in the incoming line, and hence the responsibility of the telephone service provides. Further in this regard, it is possible that one of the tip or ring lines leading to the tip and ring contacts may be inadvertently broken, disconnected or possibly improperly connected to a terminal or contact other than its intended tip or ring terminal or contact.
Accordingly, it is a general object of the invention to provide a novel and improved in-line, switched telephone line tester for quickly and easily testing for the proper tip-ring voltage and polarity of an incoming line at a modular telephone jack input to inside equipment such as PBX system. In this regard, by "in-line" is meant that the tester may be placed in the modular telephone jack and will additionally accept a mating modular telephone plug of the incoming line, so that the PBX system may be simultaneously connected with the incoming line through the tester. By "switched" is meant that testing of the incoming line may be accomplished when desired by "switching" a test portion of the tester into circuit therewith.
Broadly speaking, the concept of testing of the tip-ring polarity of telephone receptacles or modular jacks is known, as shown for example in U.S. Pat. No. 4,209,671 to Charles, et al. and U.S Pat. No. 4,373,120 to McDonald. The devices of both of these patents utilize as an indicator a lamp or other light-emitting element of a type which requires that a further element such as a diode be additionally connected or coupled across the tip-ring lines during testing. This is done to complete the circuit and/or to assure that only the proper polarity of the tip-ring voltage will cause the indicator lamp or other element to light.
Additionally, the device shown in the patent to Charles et al. further includes a battery for testing the phone jack even in the absence of a connection thereof to the central office. This battery is intended to replace the tip-ring voltage normally provided from the central office or other outside equipment. Accordingly, the device of Charles et al. can test only for continuity of the wiring or proper connection of the tip-ring wires or lines, and not for the presence and proper polarity of the tip-ring voltage from the central office or other outside equipment.
The Charles et al. device further requires that the additional diode mentioned above be coupled to the line at some point removed from the modular jack or receptacle being tested. For example, the disclosure suggests connecting this diode near a station protector located near the entrance of the phone line to the subscriber's location or even back at the central office location. Moreover, the device of the Charles et al. patent is intended for use only as a test device and must be disconnected from the line prior to connection of other telephone equipment therewith. That is, there is no provision for connection of other telephone equipment to the line when the test device is connected therewith.
The McDonald patent additionally requires that a resistor element of a predetermined value be coupled in circuit with the diode and light emitting device (which is disclosed as the neon tube) so as to provide a characteristic "signature" or signal. This latter signal is recognizable by the telephone central office equipment for purposes of making a continuity test on a subscriber line from the central office. Hence, the McDonald patent does not comtemplate on-site testing of the incoming line. Additionally, while the McDonald device permits connection of a normal telephone receiver to the modular jack with the testing device in place, the disclosure indicates that the testing device will not operate when a ringing voltage is applied to the line if a telephone receiver ringing circuit is connected to the line.
Moreover, neither of these patents discloses a switched tester apparatus. That is, the disclosed devices proceed to carry out the telephone line test and give appropriate indication when plugged into the receptacle or modular jack. These patents do not contemplate any means for selectively testing the tip-ring contacts only at periodic intervals or only when desired. In contrast, the tester of the invention is further a switched device as indicated above, such that the testing portion thereof may be switched into and out of circuit with the tip-ring contacts as desired. In view of the switched, in-line nature of the tester of the invention, it may advantageously be left coupled intermediate a modular jack of the PBX system and the modular plug of the incoming telephone line at all times, with the test indication only being given when desired.